Not quite as fancy as a kinect as I don't have £120 to buy one or any spare depth sensing cameras around. This instead works with a cheap headset mic and a £10 webcam with crude audio frequncy analysis stuff and webcam chroma-key based steering wheel tracking.

I got an idea (although i'd have no idea how to implement it) on the top and bottom of your steering wheel, you could have a similar tracker that recognises when the top is tilted forward (accelerate) or when the bottom is tilted forward (brake)
That way, you wouldn't lose speed when you get out of breath